Bicycles have been and continue to be used by many for transportation, recreation and competition. Conditions on the road and off-road place demands on a rider's body, which may result in fatigue, discomfort and soreness. It is essential, then, that a rider be able to configure his bike to best accommodate his body and the frame. Needs exist for a means to easily and quickly adjust the static frame geometry.
In recent years, mountain bike suspension devices have expanded in variation and complexity, generating widespread interest and acceptance. Competitors in the sport need bicycle frames that reduce forces on the bike and shock to the rider. Off-road conditions increase the physical demands on a rider's body, thereby speeding fatigue and increasing discomfort. Needs exist for energy-absorbing apparatus for bicycles that reduce rider discomfort and fatigue and lessen frame loads.
Existing suspension devices have proven problematic. State-of-the-art suspension units fail to maintain the basic bicycle geometry. Critical spatial relationships, such as the distance between the seat and the pedals and frame angles relative to the wheelbase, are sacrificed in efforts to enhance comfort and reduce frame loads and rider fatigue. Current bicycle frames use rear wheel suspensions for absorbing energy. Rear wheels are trailing linked and sprung such that the wheels change relative to the static geometry of frame and wheel assemblies when energy is absorbed, compromising pedaling and braking efficiency. Seats may be sprung relative to the frames, but that results in undesirable seat/pedal distance variations. Other suspension designs, such as flex-stem handlebars, strut-type energy absorbing forks, and flex frames, are hindered by similar critical relationship flaws.
Needs exist for bicycle frames that do not compromise critical geometry when suspension devices are incorporated. Since weights of riders are typically six times that of bicycles, frequent and abrupt suspension movements and subsequent changes in bicycle geometry can decrease rider control, as well. Suspension systems that eliminate or substantially limit changes in the critical relationships of bicycle components are needed to enhance efficiency and control.
Suspensions need to be simple, sturdy and not susceptible to failure. Since off-road conditions are not constant, needs exist for suspension devices that are adjustable and easily customized by riders. Energy-absorbing mechanisms need to be compatible with conventional frame configurations and adaptable to newly designed lightweight frames.